DESCRIPTION: This study seeks to better understand the role of economic factors in explaining mortality patterns, particularly in low-income populations. Our focus is on the role of the health insurance system, and more specifically, how large changes in the health insurance coverage of a population might influence mortality. In order to synergistically begin to build a body of empirical regularities, we propose to analyze the causal effects of actual large insurance expansions in different settings. One set of analyses will examine the mortality effects of the implementation of the Medicare and Medicaid programs in the United States during the 1960's, which have received surprisingly little study. A parallel set of analyses will build on previous work examining a large expansion in insurance coverage in Costa Rica during the 1970's. The project also includes a methodological investigation of the effects of the common practice of analyzing regionally aggregated mortality data instead of individual-level micro data. This project is expected to yield important new information in understanding the effect of health insurance on mortality patterns themselves, and on explaining socioeconomic differences in health. This knowledge is important not only for these two countries, but for many other countries as well as they debate large-scale reforms of their health insurance systems.